Sound-damping lens adapter for a motion-picture camera

Abstract

This adapter is interchangeable with standard nondamping lens-mounting adapters. It reduces the amount of vibration that is transmitted from the camera mechanism to the lens. It thereby reduces the amount of vibration that is retransmitted as objectionable background sound, by radiation from the lens, into a sound stage or other scene area. A vibration-absorbing resilient ring is securely fixed to two substantially rigid rings. A camera mount is secured to one of the rigid rings, for mounting to a camera in a normal position for mounting a standard adapter. A lens attachment is secured to the other rigid ring, for attachment to a lens in a normal position (on the lens) for attaching a standard adapter. The camera mount and the lens attachment both have respective standard-configuration portions, which are spaced apart by a distance that is precisely equal to a standard distance between the respective corresponding portions of a standard adapter. Hence the resilient ring absorbs a fraction of the objectionable noise vibration, deterring that fraction from being transmitted to and radiated from the lens into the scene area--but does so while maintaining a standard distance between the lens and the camera focal plane, and without modification of either the lens or the camera.

We claim: 
     
       1. A sound-damping adapter for use in place of a standard nondamping adapter in mounting a lens to a motion-picture camera, such a camera being subject to generation of objectionable noise vibration, and such a lens being subject to transmission and radiation of such noise vibration from the camera into a scene area; and adapter comprising: a first substantially rigid ring;   mounting means, secured to the first ring, for mounting the first ring to such a camera, substantially outside such camera, in a normal position for mounting such a standard adapter; said mounting means including a portion that has a standard configuration of such a standard adapter for such mounting;   a second substantially rigid ring;   attachment means, secured to the second ring, for attaching the second ring to such a lens, in a normal position for attachment of such a standard adapter; said attachment means including a portion that has a standard configuration of such a standard adapter for such attachment;   a vibration-absorbing resilient ring securely fixed to the first and second rings and deterring transmission of vibration from the first ring to the second ring;   the respective standard-configuration portions of the mounting and attachment means being spaced apart by a distance that is precisely equal to a standard distance between the respective corresponding portions of such a standard adapter;   wherein in operation the resilient ring absorbs a fraction of such objectionable noise vibration, deterring such fraction from being transmitted from the normal standard-adapter mounting position to such lens, and from being radiated from such lens into such scene area, but while maintaining a standard distance between such lens and such camera focal plane and without requiring any modification of either such lens or such camera.   
     
     
       2. The adapter of claim 1, wherein: the resilient ring is sandwiched between the first and second rings.   
     
     
       3. The adapter of claim 2: wherein one of the two rigid rings defines a plurality of smooth longitudinal apertures;   further comprising a plurality of support pins fastened to the other of the two rigid rings, projecting longitudinally through the resilient ring, and sliding longitudinally in a close but smooth fit in the apertures defined in said one rigid ring;   wherein the relative longitudinal positioning of the rigid rings is controlled only resiliently by the resilient ring; and   wherein the support pins and the resilient ring in combination fix the relative positioning of the rigid rings only transversely.   
     
     
       4. The adapter of claim 3, wherein: the resilient ring is of an elastomer whose durometer is approximately forty;   the second ring is of a relatively heavy metal;   the attachment means include threaded inserts of a hard metal such as steel, anchored in the second ring, to threadingly receive mounting screws passed through the attachment means;   the resilient ring is self-bonded to the first and second rings by application of pressure and heat; and   the support pins are of a material that is resistant to pressure and heat at the pressures and temperatures used for said bonding; and   further comprising first and second securing means for securing the mounting and attachment means to the first and second rings respectively, the securing means being configured so that they do not significantly press into the elastomer of the resilient ring.   
     
     
       5. The adapter of claim 4, wherein: the second ring is of lead; and   the support pins are of the acetal resin available commercially under the trade name Delrin.   
     
     
       6. The adapter of claim 1, for use with such a camera that has a built-in sound-damping assembly for attachment of lenses; such built-in assembly including a block that has a lens-receiving fitting secured to a resilient vibration absorber; and wherein: the mounting means are particularly configured for mounting to such built-in sound-damping assembly so that the assembly and the adapter together form a multiplicative two-stage filter for sound vibration;   whereby in operation such objectionable sound vibration is attenuated in two multiplicative stages to a particularly low residual level.   
     
     
       7. The adapter of claim 3, for use with such a camera that has a built-in sound-damping assembly for attachment of lenses; such built-in assembly including a block that has a lens-receiving fitting and is secured to a resilient vibration absorber, and that is supported by a plurality of support pins which are fixed to the camera and slip in a close but smooth fit in apertures defined in the block; and wherein: the mounting means are particularly configured for mounting to such built-in sound-damping assembly so that the assembly and the adapter together form a multiplicative two-stage filter for sound vibration;   whereby in operation such objectionable sound vibration is attenuated in two multiplicative stages to a particularly low residual level.   
     
     
       8. The adapter of claim 4, for use with such a camera that has a built-in sound-damping assembly for attachment of lenses; such built-in assembly including a block of a relatively heavy metal, that has a lens-receiving fitting and is secured to a resilient vibration absorber, and that is supported by a plurality of support pins which are fixed to the camera and slip in a close but smooth fit in apertures defined in the block; and wherein: the mounting means are particularly configured for mounting to such built-in sound-damping assembly so that the assembly and the adapter together form a multiplicative two-stage filter for sound vibration;   whereby in operation such objectionable sound vibration is attenuated in two multiplicative stages to a particularly low residual level.   
     
     
       9. The adapter of claim 1, in combination with: such camera.   
     
     
       10. The adapter of claim 3, in combination with: such camera. 
     
     
       11. The adapter of claim 4, in combination with: such camera. 
     
     
       12. The adapter of claim 6, in combination with: such camera. 
     
     
       13. The adapter of claim 1, in combination with: such lens, in the form of a zoom lens having a relatively large forwardmost optical element that is particularly subject to efficient transmission into such scene area of any such sound vibration that reaches the zoom lens;   wherein the absorption of such noise by the resilient ring, before such noise reaches the zoom lens, minimizes radiation of such objectionable noise vibration into such scene area despite efficient transmission by the zoom lens.   
     
     
       14. The adapter of claim 3, in combination with: such lens, in the form of a zoom lens having a relatively large forwardmost optical element that is particularly subject to efficient transmission, into such scene area, of longitudinal sound vibration that reaches the zoom lens;   wherein partial mechanical isolation of the first and second rings by the resilient ring, with respect to relative longitudinal vibration, and the partial absorption of such longitudinal noise vibration by the resilient ring before such vibration reaches the zoom lens, minimize radiation of such objectionable noise into such scene area despite efficient transmission and radiation by the zoom lens; and   wherein fixed mutual positioning of the first and second rings by the support pins and resilient ring in combination, with respect to relative transverse motion, maintains optical alignment of the zoom lens relative to the camera.   
     
     
       15. The adapter of claim 4, in combination with: such lens, in the form of a zoom lens having a relatively large forwardmost optical element that is particularly subject to efficient transmission into such scene of area of any such sound vibration that reaches the zoom lens;   wherein mechanical isolation of the first and second rings by the resilient elastomeric ring, and the absorption of such noise by the resilient elastomeric ring before such noise reaches the zoom lens, minimize radiation of such objectionable noise vibration into such scene area despite efficient transmission by the zoom lens; while mutual orientation of the first and second rings by the resilient elastomeric ring and support pins maintains optical alignment of the zoom lens relative to the camera.   
     
     
       16. The adapter of claim 6, in combination with: such lens, in the form of a zoom lens having a relatively large forwardmost optical element that is particularly subject to efficient transmission into such scene of area of any such sound vibration that reaches the zoom lens;   wherein radiation of such objectionable noise vibration into such scene area is minimized by the multiplicative two-stage attenuation despite efficient transmission by the zoom lens.   
     
     
       17. The adapter of claim 7, in combination with: such lens, in the form of a zoom lens having a relatively large forwardmost optical element that is particularly subject to efficient transmission into such scene of area of any such sound vibration that reaches the zoom lens;   whereby radiation of such objectionable noise vibration into such scene area is minimized by the multiplicative two-stage attenuation despite efficient transmission by the zoom lens.   
     
     
       18. A low-noise cinematographic system comprising: a substantially conventional motion-picture camera that is subject to generation of objectionable noise vibration, and that has a substantially conventional built-in sound-damping assembly for attachment of lenses; the built-in assembly including a block that has a lens-receiving fitting and is secured to a resilient vibration absorber, for reducing transmission of the camera-generated vibration to such lenses;   a sound-damping adapter, substantially outside the camera, mounted to the lens-receiving fitting of the built-in sound-damping assembly so that the assembly and the adapter together form a multiplicative two-stage filter for noise vibration; and   a substantially conventional lens, mounted to the sound-damping adapter, that radiates a portion of noise vibration which reaches the lens;   whereby in operation the multiplicative vibration filter formed by the assembly and adapter together minimizes the amount of such noise vibration from the camera that reaches the lens, and so minimizes the amount of vibration radiated by the lens.   
     
     
       19. The system of claim 18, wherein: the lens is a zoom lens with a relatively large forwardmost optical element that is particularly efficient in radiating vibration into a scene area that is being photographed; and   the multiplicative vibration filter reduces the amount of noise vibration reaching the lens from the camera, and therefore the radiated noise vibration, to an acceptable residual level despite the efficiency of the lens in radiating such noise.   
     
     
       20. The system of claim 18, wherein the adapter comprises: a first substantially rigid ring;   mounting means, secured to the first ring, for mounting the first ring to the lens-receiving fitting, substantially outside the camera;   a second substantially rigid ring;   attachment means, secured to the second ring, for attaching the second ring to such a lens; and   a vibration-absorbing resilient ring, securely fixed to the first and second rings, for absorbing a fraction of such noise vibration generated by the camera and affecting the lens-receiving fitting, and so deterring the fraction from being transmitted to the lens.   
     
     
       21. The system of claim 20, wherein the lens has conventional standard focal properties establishing a required distance between the lens and a focal plane within the camera; and wherein: the sound-damping adapter is sized and configured to replace a conventional nondamping adapter and is mounted to the camera lens-receiving fitting, without modification of the camera or fitting, in a normal position for mounting such a conventional adapter;   the mounting means include a portion that has a standard configuration of such a standard adapter for such mounting;   the sound-damping adapter is attached to the lens, without modification of the lens, in a normal position for attachment of such a conventional adapter;   the attachment means include a portion that has a standard configuration of such a standard adapter for such attachment; and   the respective standard-configuration portions of the mounting and attachment means are spaced apart by a distance that is precisely equal to a standard distance between the respective corresponding portions of such a standard adapter;   whereby the sound-damping adapter reduces the amount of noise vibration radiated from the lens into a scene area, while maintaining a standard distance between the lens and the camera focal plane and without any modification of either the lens or the camera.   
     
     
       22. The system of claim 21, wherein: at least one of the two rigid rings is of a relatively heavy metal and defines a plurality of smooth longitudinal apertures;   the sound-damping adapter further comprises a plurality of support pins fastened to the other of the two rigid rings, projecting longitudinally through the resilient ring, and sliding longitudinally in a close but smooth fit in the apertures defined in said one rigid ring;   wherein the relative longitudinal positioning of the rigid rings is controlled only resiliently by the resilient ring; and   wherein the support pins and the resilient ring in combination fix the relative positioning of the rigid rings only transversely.   
     
     
       23. The adapter of claim 22, wherein: the resilient ring is of an elastomer whose durometer is approximately forty;   the second ring is of a relatively heavy metal;   the second securing means include threaded inserts of a hard metal such as steel, anchored in the second ring, to threadingly receive mounting screws passed through the attachment means;   the resilient ring is self-bonded to the first and second rings by application of pressure and heat; and   the support pins are of a material that is resistant to pressure and heat at the pressures and temperatures used for said bonding; and   the sound-damping adapter further comprises first and second securing means for securing the mounting and attachment means to the first and second rings respectively, the securing means being configured so that they do not significantly press into the elastomer of the resilient ring.